I think Improved Familiar (Beguiler - from Shining South) is both good and flavorful

Best,David

And helpful. I've got a New Years game that I am making a Beguiler for right now. Big group so I'm not looking to optimize too much (aside from being dragonwrought )

Going to be 7th level and I think I have settled on Versatile Spellcaster, Dragonwrought, Obtain Familiar, Enspell Familiar, and Celestial Familiar (Coure Eladrin) for the feats. Beguiler as a familiar certainly crossed my mind

Now if only I get to play it. It is one of 10 pregenerated characters we are going to have for the group.

Beguiler 8/Shadowcraft mage 5 build isn't valid - Shadowcraft mage has a prereq of having shadow spell of 4th or higher level and Beguiler list doesn't have one until 6th spell level. So either you should take PrC after 12 (11 if you use Advanced Learning for learning shadow spell) levels of Beguiler or use other PrCs to delay Advanced Learning on 7th class level.

Beguiler8/SCM5 works fine. Legion of Sentinels is a 3rd level Shadow spell on the Beguiler's list. With the Heighten Metamagic feat you would be able to cast it as a 4th level Shadow spell thus qualifying.

And of course as a Shadowcraft Mage you most likely WILL have Heighten Spell.

First off I'd like to thank you, this guide is wonderful.Secondly, wouldn't the rainbow servant prestige class be viable with the beguiler if you invest a bit into wisdom? The 10 levels are a pretty big dip but personally, I think it's worth it.

I'm not an expert, but it seems to me that Sand Shaper PRC work very nicely with the Beguiler. You loose a level in your spell progression (or two if you take the whole thing), but you gain a significant number of spells known, along with some unusual abilities.

I use early entry tricks to reach Rainbow Servant @2. I take all 10 levels due to needing an Illusion (Shadow) spell of level 4 or higher, which Clerics get. (A Heightened dark way qualifies, as does a plain ol' skull of secrets spell.) Shadowcraft Mage5 is just because, well, Shadowcraft Mage, and provides a thematic power boost. I included Mindbender1 due to it just rocking.

I'm tempted to say "Include Archmage in this build!" because it sounds cool and it didn't originally seem possible, but its 2 additional feat prereq turns me off. (Those feats could instead be used on Shadowcraft Mage goodiness!)

Rearranging things and going Mage of the Arcane Order doesn't seem worth it due to it costing 2 additional feats (Arcane Preparation and Cooperative Spell) OR one additional level 1-only feat, Magical Training. (Magical Training also requires your GM being OK with using this feat for entry.)

Incantatrix is a very tempting inclusion for this build, for it is effectively the best general arcane casting PrC there is in 3.5. Mystic Theurge is possible but cheesy due to Rainbow Servant10 granting access to the entire Cleric spell list... as Divine spells known... on the same class list (Beguiler) that also casts arcane spells. What else do you suggest?